@RiversideBryan

Would love to see one. Lovely bird/pic.

It looks like it may be some sort of algae. Was there a strong glare on the water? The glare may have caused your camera to compensate. Water is weird because if you compensate for glare it often reveals features that you couldn't see at the time.

Could also may be compensating for the strong contrast between bird and water. It may have tried to knockout the strong highlights on the bird and darkened the water in the process.

@RiversideBryan

Sounds like it was compensating for the glare. Photographers used to (and probably still do) put a polarized filter on their camera when they shoot near water or at clouds. I have an editing feature that allows me to do the same without using a filter. Comes in handy for when I photograph fish under water.

Love to hear that and see one! Not much in the way of cranes and herons near me. I think I'd have to head over to the Mississippi to see some.